γ‐Ray Regulated Host–Guest Molecular Recognition

ABSTRACT Decades of advances in light‐responsive host–guest supramolecular systems allow precise molecular switching and photoactivation, yet their in vivo use is severely limited by the weak tissue penetration of UV/visible light. Ionizing radiation such as γ‐rays possesses outstanding deep‐tissue penetration, which has been widely applied in clinical radiology and radiotherapy. Herein, we develop a γ‐irradiation‐regulated host–guest recognition system based on azobenzene derivatives and macrocyclic hosts (cyclodextrins and cucurbiturils). At a clinical dose of 2 Gy, γ‐radiation triggers cis‐to‐ trans isomerization of azobenzene and enables efficient molecular recognition with macrocycles. γ‐Rays outperform blue light in inducing isomerization even through centimeter‐thick porcine tissues, and the system exhibits excellent recyclability over ten irradiation cycles. Moreover, γ‐ray‐regulated ternary recognition realizes in situ hydrogelation, constructing double‐network hydrogels with simultaneous mechanical reinforcement, stiffening and self‐healing. The hydrogel achieves tensile strength of ∼23 MPa and toughness of ∼30 MJ m −3 , comparable to engineered elastomers while retaining supramolecular adaptability. This radiation‐regulated molecular recognition offers a universal platform for remotely programming soft material mechanics and holds great potential for in vivo applications.